h screw

I'm tuning a 2004 Husqvarna 55 Rancher. Just rebuilt the carb and am adjusting the mixture. When adjusting the H screw I found I could not get the RPMs to drop down below 13,000 (spec. is 12,500). At one point I had the H screw backed out 4 complete turns but the RPMs were still over 13,000. The...